To define the nature and extent of influenza (and other respiratory pathogens) associated Severe Acute Respiratory Infection (SARI) amongst urban and rural high-risk adults and children in Malawi in an area with highly endemic malaria and a high HIV prevalence. In the context of circulating influenza viruses, this work will focus SARI amongst those children under 1 year old, pregnant mothers and HIV infected adults admitted with and without malaria to a large Central Hospital in urban Malawi (Blantyre) and a rural site (Chikhwawa). The proximity of a MLW research facility based in Cikhwawa with a high malaria burden to the main MLW laboratory in Blantyre, provides a unique opportunity to make comparisons between rural and urban, and high and low malaria endemic populations.